Visas & Invitation Letters


As you know, the requirements for travel to the United States constantly change. The links below can connect you to the latest US Government Visa information. We urge everyone that requires a Visa to travel to the US to apply for the Visa as early as possible. Please read the following information carefully.

  • Apply at the appropriate location at least 5 months before intended travel. You can check on-line for the wait times for appointments.
  • Be prepared to allow inkless fingerprinting and digital photographs upon entry to the US.
  • Be accurate and specific in completing your application. Avoid mistakes. If needed, attach an additional explanation letter.
  • Attach evidence of your previous visits to the United States and of your intended return trip to your home country.
  • Acquire a police clearance, if possible.
  • Bring all documentation proving your home country connections. Suggestions include: past visas, bank accounts, family, professional position, home ownership, and marriage license.
  • If you are presenting a paper or speaking at the meeting or are receiving and award or grant, bring copies of correspondence confirming that.
  • Bring your letter of invitation.

Click here for information on Temporary Visas to participate in a meeting or other temporary travel to the United States.

Note: A Visa only allows you to travel to the US. You will still have to be admitted at your point of entry. Click here for information from Homeland Security on the Entry Process.

Invitation Letters

If you require a letter of invitation for your visa application, please submit a request for a letter of invitation.

At least one of the following criteria must be met in order to honor the request for a letter of invitation. The requesting party must either:

  1. Be an author of an accepted abstract and/or paper.
  2. Have paid the advanced registration fee for this conference.
  3. Have paid the advanced registration fee in full and are not from one of the countries embargoed by the U.S. Treasury Department's Office of Foreign Assets Control.

Important: All letters of invitation will be sent via regular mail unless you provide a Federal Express or DHL account number. In most cases, Visa Offices will not accept faxed or e-mailed invitation letters.

Please provide the following information in your request:

  • Your full name (Please specify family name and given name)
  • Title (Dr., Professor, Mr., Mrs., Miss, Ms, etc.)
  • Organization
  • Full mailing address
  • Telephone and Fax numbers
  • Email address
  • Additional information such as if you are presenting a paper at the Conference

To request a letter of invitation:

Click here for a description from U.S Customs and Border Protection of the process for entering the United States.

The National Academy of Science has established an International Visitors Office with travel information specifically designed for scientists traveling to the US.